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Energy Costs Put Focus on Kiln Heat Recovery
By Jack Petree - Contributing Author
Date Posted: 3/1/2001
Wooddryer Systems/Kiln-Direct Already Has Track Record in Heat Recovery Technology for Dry Kiln Operations
Soaring energy prices are likely to prompt sawmills and related businesses with drying operations to scrutinize their dry kiln technology in order to rein in energy costs. Soaring prices for electricity have helped to drive up the price of diesel, gas, and other fuels, all of which were already on a steep upward spiral. The soaring energy costs will prompt mills to focus on and demand kiln drying technology that reduces or controls energy costs, according to a supplier of dry kiln technology.
North Carolina-based Niels Jorgensen Inc. already is well positioned to help mills that are faced with escalating energy costs, according to its president, Niels Jorgensen. He and his father and their companies have been busy pursuing heat recovery technology for more than 15 years.
The soaring energy prices are putting the spotlight on energy consumption of kiln operations, noted Niels. Kiln suppliers will argue that their systems do not use that much energy. In the real world, however, a large part of the cost of operating a kiln is in heating the air used to dry the wood. Mills that may spent millions of dollars on incremental improvements in optimizing their operations may have ignored their drying operations. Lulled into a false sense of complacency by the lack of urgency regarding kiln improvements, few have done much about controlling the energy costs of their drying operations. Compounding the problem, according to Niels, is that there is little accurate information available about the technology to help them.
These mills, as well as kiln manufacturers that are not paying attention to advances in technology, are in for a shock. Niels believes the soaring energy costs will prompt mills to focus on and demand kiln drying technology that reduces or controls energy costs.
Energy costs associated with dry kilns can be controlled, according to Niels, by systems like those the Jorgensens have been developing the past 15 years. The company’s technology recovers and reuses heat from the hot, humid air inside the kiln — heat that normally is wasted by other drying systems when the humid, warm air is exhausted outdoors.
Vald Jorgensen, president of Jorgensen International in Denmark, and Niels have been responsible for the design and installation of more than 500 kilns on three continents in the span of about 20 years. Their companies have worked for small mills as well as some of the world’s leading lumber manufacturers. Their commitment, according to Niels, is to "deliver a highly reliable system that meets all of today’s specifications and offer it to the lumber industry at honest pricing."
As the adage goes, ‘If you build a better mousetrap, the world will knock at your door." When Vald inherited his father’s sawmill in Denmark several decades ago, he learned how to dry very sensitive woods better than almost anyone else in the country, and customers from around the world sought the company’s lumber products.
Challenged by the need to properly dry very light-colored woods, especially beech, while maintaining them in perfect color, Vald set to work to design a kiln system and controls that would make his lumber the finest in the world.
Vald, who had a background in electrical automation before taking over the family business, was successful with the drying technology that he developed. His peers in the Danish forest products industry began to seek his advice about drying the fine woods his country is known for. As Niels tells it, Vald began to restructure his business, transforming it into a company focusing on the sale of the Jorgensen-designed kiln technology.
The companies remain committed to the kind of innovation that Vald displayed when he first ventured into lumber drying. However, lumber drying technology overall has suffered from a lack of competitive innovation in lowering energy costs in recent decades, according to Niels. Heat recovery is an area that has been seriously neglected, especially by American manufacturers, he said. It is an area that likely will receive increasing attention, though, as energy costs continue to soar.
"There has been little innovation in the standard kiln design during the last several decades," said Niels, who recently addressed industry academics in Hungary. While there have been interesting and promising advances, they have not had much influence in the industry, according to Niels. He compared the advances to the Concorde airplane, an airship that incorporated bold new technology but it has not had much influence on the passenger transport industry as a whole.
An important reason for the lack of true innovation in the industry, Niels contended, is that most of the competition between kiln suppliers is on the basis of price. Many suppliers do not differentiate themselves in terms of kiln system design or construction features that actually improve a mill’s ability to dry lumber — at a reasonable price. "In the kiln manufacturing industry today," said Niels, "we have a good system for competing on price, but we have failed greatly in creating competition on improving kiln design that will provide a better drying result."
Niels sees change coming, however. In the future, kiln manufacturers will have to bring innovations to the market if they want to remain competitive because mill owners are beginning to see that improvements are possible. Customers will demand innovation, especially to lower energy costs.
The heart of the Niels Jorgensen Wooddryer Systems/Kiln-Direct heat recovery unit is an air-to-air exchanger that has been developed specifically for lumber kilns. The heat recovery unit is fabricated of stainless steel with aluminum in the heat transfer area; aluminum components maximize heat recovery while stainless steel ensures durability.
Generally, kilns draw in fresh air from outside and heat it, which makes the air capable of holding more moisture. The heated air passes over the wood. As it does, the imbalance between the moisture content of the wood and the dry air causes the moisture to move out of the wood and is absorbed by the air. When the air becomes humid and cannot hold any more moisture, it is exhausted from the kiln. Fresh air is drawn in again, and the process starts over.
These systems are inefficient because a lot of heat is lost when the warm, moist air is dispelled, and energy is used to heat more fresh air. The moist air still is hot when it is vented from the kiln. If that heat can be recovered from the moist air before it is exhausted and used to heat fresh air, energy costs can be reduced significantly.
The Niels Jorgensen system for heat recovery takes the hot, humid air exiting the kiln and first passes it through an aluminum exchanger. The hot air heats the aluminum exchanger as it passes by. At the same time, incoming fresh air is passed over the other side of the exchanger, which warms it up. So heat is removed from the exiting moist air and is used to warm the incoming fresh air. Since the incoming fresh air is now substantially warmer, less energy is required to finish heating it to the temperature required for the kiln operation.
The impact of heat recovery in dry kiln operations can be dramatic. In a recent test carried out in Denmark, the effectiveness of the Jorgensen heat exchange system was compared in kilns of similar size and drying identical wood products; some kilns were equipped with the Jorgensen heat exchange system and others were not. The kilns equipped with the Jorgensen heat exchange system saved 33% in energy costs compared to the kilns without it, according to Niels. The savings amounted to $733 per 100,000 board feet of green lumber dried.
While the ability to reduce the amount of energy used for drying operations is vital for reasons economic, environmental, and social, it may represent only the tip of the iceberg. Heat exchange systems can reduce capital costs, increase drying production, and achieve other efficiencies, Niels noted.
Companies can save on capital costs because the greater efficiency of the heat exchange system allows for significantly more wood to be dried with the same amount of energy. According to Niels, a mill operating kilns fired by wood waste or any other fuel and running at near capacity can begin to dry as much as 40-50% more wood. A heat exchange system eliminates the capital expense of increasing the boiler capacity. A mill can increase production of dry lumber without the extra large capital expense of adding more boiler capacity.
The heat exchange system also adds adequate venting of the kiln. Heat recovery along with improved temperature control generally allow throughput to be increased.
Increased production means increased profits, Niels noted.
The Jorgensen Wooddryer Systems/Kiln-Direct heat recovery system can generate sufficient savings to pay for itself within 7-10 months on fast drying species, especially if a mill is drying fresh sawn lumber in its kiln, Niels said. The payback varies with kiln design, location, species of wood, and many other variables, he noted. However, companies with standard, conventional kilns, like those used in most high-volume drying operations, certainly benefit — and benefit greatly — from the addition of a heat recovery system, said Niels.
Mill managers also can begin to control some of the operating costs associated with a dry kiln by taking a few easy steps to improve their maintenance programs, Niels suggested. These steps include:
• Inspect the main kiln doors to make sure that gaskets seal the door tightly against the door frame. If you can see daylight from inside the kiln with the doors closed, energy — and money — is being wasted.
• Check the effectiveness of the insulation in the main kiln doors by feeling the door with your hands. If you can feel warm spots, heat is escaping, and energy is being wasted.
• Look at the condition of the wall and roof, especially where they meet. Apply kiln coating if necessary. Damage to masonry or panel walls should be repaired.
• Evaluate the heating system to ensure it is working efficiently.
• Examine the vents. When they are closed, there should be no daylight visible from inside the kiln.
This maintenance may seem routine and commonsense, but Niels has looked at a number of kilns where companies were lax when it came to these steps. And these kind of defects can significantly increase the cost of operating a kiln, he noted.
While mill managers in the past may not have felt special urgency to reduce energy costs in their kiln operations, the efficient, profit-minded manager of the future will have to pay very close attention to energy, Niels contended. "Energy costs will continue to increase, and although we are probably not likely to have European energy prices anytime soon, heat recovery systems will certainly become more attractive in both new kiln operations and as an upgrade to existing kilns. Improved drying quality with lower energy consumption is a concept that cannot be ignored any longer in a profit-minded mill."
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